The present invention relates to a method and an apparatus for producing a flat spiral link assembly in which left-hand and right-hand heices are alternately meshed and interlocked by pintle wires so that each pintle wire is disposed in the passages formed by the overlap of at least three helices. The helices are produced from synthetic resin monofilament and conventionally have an oval cross section.
According to German Patent DE-A No. 2,938,221, the helices generally do not exhibit any tension or compression spring bias, i.e., when taken out of the assembly they retain the pitch they have in the spiral link assembly. Spiral link assemblies in which each pintle wire is disposed in the interior of at least three helices or, in other words, in which at least three pintle wires are disposed in the interior of each helix are known from EP-A No. 18,200; GB-A No. 19,045; DE-A No. 3,416,234; U.S. Pat. No. 3,300,030; and U.S. Pat. No. 3,308,856, and DE-A No. 3,402,620. A similar spiral link assembly is known from U.S. Pat. No. 3,563,366, but in this patent all the helices are wound in the same sense of direction and the winding arcs of the helices are mutually intertwined, thereby holding between them the pintle wire.
Helices made of synthetic resin monofilament are normally wound in closely packed windings since only in this state can they be stored in cans or containers. They have a pitch corresponding to twice the diameter of the synthetic resin monofilament. If helices are made with a higher pitch, there is the risk that they will become inextricably entangled in the storage container. While conventional spiral link belts, such as disclosed in German De-A No. 2,938,221, in which each helix encloses only two pintle wires, can be made from narrowly wound helices and also from helices having a pitch corresponding to twice the diameter of the synthetic resin monofilament, i.e., a pitch which later on results automatically in the spiral link belt, spiral link belts in which each helix encloses at least three pintle wires cannot be made from narrowly wound helices since the meshing helices would develop such a high contractive force that after assembly they could only be shifted relative to their longitudinal axes with great difficulty and then the insertion of the pintle wires into spiral link belts of greater width would become impossible. For such spiral link belts it therefore has hitherto been possible only to produce the helices on the winding machine with accordingly high pitch and then to directly feed the helices to the assembling device where the helices are then meshed. Intermediate storage was not possible because then the helices would have become entangled in an inextricable mess.
Apparatus for meshing a plurality of helices and for inserting the pintle wires are known from EP-A No. 36,972 and EP-A No. 54,930, and WO No. 82/03097. However, in these embodiments each pintle wire connects only two helices each. These apparatus are not suited to produce spiral link assemblies from helices of high pitch, i.e., of spiral link assemblies with three or more pintle wires passing through each helix.